1. Field of the Invention
The present invention relates to catalyst compositions and to processes for preparing interpolymers of olefins and carbon monoxide by polymerising a mixture of one or more olefins and carbon monoxide in the presence of such catalyst compositions. In particular, the present invention relates to novel compounds and their use as catalysts in such processes.
2. Description of the Related Art
The preparation of linear alternating interpolymers of olefins and carbon monoxide having the formula: ##STR1## where the R groups are independently hydrogen or hydrocarbyl groups, n is at least 1 and m is a large integer, is known from U.S. Pat. No. 3,694,412. Such linear alternating interpolymers, which hereafter will be called polyketones, are prepared according to U.S. Pat. No. 3,694,412 by polymerising a mixture of one or more olefins and carbon monoxide in the presence of an aryl phosphine complex of a palladium halide and an inert solvent. However, the processes described in U.S. Pat. No. 3,694,412 are slow even at elevated temperature and pressure.
An improved version of the process described in U.S. Pat. No. 3,694,412 is described in European patent applications 181014 and 121965. It was subsequently found that the rate of the polymerisation process could be increased considerably by using a palladium catalyst with inter alia a bidentate phosphine and the anion of a carboxylic acid having a pKa of lower than 2 (as measured in aqueous solution). Examples of anions which can be used include trichloroacetate, dichloroacetate, tetrafluoroborate, hexafluorophosphate and p-toluene sulphonate, such anions being respectively the conjugate anions of trichloroacetic acid (pKa 0.70), dichloroacetic acid (pKa=1.48), tetrafluoroboric acid, hexafluorophosphoric acid and p-toluenesulphonic acid.
More recently EP 222454 suggests that any acid having a pKa of less than 5 (determined in aqueous solution at 18.degree. C.) can be used.